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Nelson's Column EarthCache

Hidden : 2/18/2014
Difficulty:
1.5 out of 5
Terrain:
1 out of 5

Size: Size:   other (other)

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Geocache Description:


Nelson's Column in Trafalgar Square is one of the most famous monuments in London, receiving thousands of visitors every year. It was originally conceived by John Nash in 1812 to commemorate Nelson's victory at the Battle of Trafalgar in 1805, but Trafalgar Square was not actually started until almost 30 years later to designs by Charles Barry.

The foundations for Nelson's Column were laid in 1839 and it was completed by 1843.  The whole monument is 51.6 m tall from the bottom of the pedestal to the top of Nelson's hat.  

The column itself is built of massive drums of grey Foggintor granite from Devon, with the statue itself carved from the Scottish Craigleith sandstone.  
 

Granite

Granite has long been used for its strength and durability as well as its attractive appearance. Few stone types have been used for such a wide range of purposes, from structural and engineering foundations to decorative building interiors. Granite was quarried in all corners of the British Isles, initially from coastal locations and transported by sea to the major urban centres.

The granite used in Nelson’s Column came from the Foggintor Quarry on Dartmoor in Devon.

Granite forms from the cooling of large magma bodies at depth in the crust, the slow cooling allowing the growth of large and interlocking mineral crystals. Compositionally, granites typically contain 55-75% silica and are commonly pale coloured with medium to coarse grained crystals discernable to the naked eye. The interlocking crystals provide cohesion which adds strength and makes them suitable for polishing. Finer grained granites were typically used for structural purposes (e.g. foundations, walling, kerbstones, setts and paving), while coarser grained and porphyritic (i.e. with large crystals usually of feldspar) varieties were valued for ornamental work. The predominance of silica and other relatively stable minerals in granite make it particularly strong and durable.  Granite is hard and not very porous and is composed of several different materials.

 

Sandstone

The statue of Nelson atop the column is carved from two blocks of Craigleith sandstone, obtained from the Granton Quarry in Scotland.  The first idea had been for the statue to be cast in bronze, but that was found to be too expensive. It was then decided to use Portland stone – a limestone from the south of England.  However, the statue was to be 17 feet high and it proved impossible to obtain large enough pieces of stone. The organising committee then had a sample of Craigleith stone sent to London by steamer in October 1840. There were problems in getting large enough blocks out of the quarry but this was accomplished and the stone was delivered in July 1842. After the blocks had been carved by the sculptor, Edward Hodges Baily (1788 – 1867), they were lifted into position on top of the column on 3 November 1843.

Craigleith Stone is perhaps the most durable sandstone in the United Kingdom.  It consists of quartz grains united in a siliceous cement with small plates of mica.  It contains 98% of silica and only 1% carbonate of lime.   This sandstone is much less porous than many types used in the UK and suffers little erosion in comparison.

 


Your tasks
To log this cache, you will need to complete the tasks below.  You can use information from the cache page and your observations at GZ to do this. Please message us with the info (rather than post it on your log).  You can log a find once we have been sent a message; there is no need to wait for a reply. We may delete your log if your answer is way off the mark.

  1. Granite comes in many different colours (pinks, reds, greys, creams, whites etc).  What colour is the granite used in Nelson's Column?    Are the grains in the granite fine or coarse?  Do you think that the granite chosen was the type used for ornamental or structural purposes?
  2. The statue is made of sandstone and not granite.  Why do you think this is?
  3. On 11 November 1918, on Armistice Day, thousands of people gathered in Trafalgar Square and a large bonfire was lit at the base of Nelson’s Column.  The intense heat caused the granite in one of the blocks to crack.  The cracked, distorted block can still be seen today in the centre of the base on the west side of the column.  Find this block and describe the cracks you can see. Can you explain why the granite cracked?
  4. As an optional extra, post a picture of yourself / your GPSr at Nelson’s Column.

 

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